1. Field of the Invention
The present invention relates to a transfer type each-side exposure apparatus which is arranged to transfer a plurality of materials desired to be exposed into an exposure chamber by transfer means to subject them to continuous exposure.
2. Description of the Prior Art
Various types of exposure apparatuses have hitherto been adopted in accordance with uses or purposes. When it is desired to effect a precise exposure baking, it is necessary to reproduce image lines of a document with high precision. To this end, it is desirable to use a point source of light as an exposure source of light so as to obtain paralle exposure light beams which are high in resolution. Actually, however, it is impossible to obtain a complete point source of light. Even if a light source nearly in the form of a point source of light is obtained, it is impossible to obtain an amount of light which is sufficient for performance of exposure. For this reason, a line source of light such as a high pressure mercury vapor lamp has hitherto been employed which enables a sufficient amount of light to be obtained although somewhat lengthy.
An exposure apparatus which uses a line source of light as the above-mentioned light source is disclosed in Japanese Patent Laid-Open No. 34162/85 previously filed in Japan by the Applicant of the present invention. The exposure apparatus disclosed in that literature has considerably improved the drawbacks which were produced with the use of a line source of light. When compared with the exposure baking performed with the use of the line source of light combined with a light beam control plate, the exposure baking performed with the use of the point source of light combined with a light beam control plate has a merit in that a high resolution is obtained with a simple construction but has a demerit, on the other hand, in that a large amount of exposure time is required for obtaining a sufficient amount of light necessary for exposure, resulting in a low productivity. The exposure apparatuses, with the use of which said exposure bakings are performed, each require the provision therein of transfer means for transferring material to be exposed, in order to make the irradiating amount of light uniform with respect to the materials to be exposed.
As stated above, the exposure apparatuses which use the point sources of light have a drawback in that they are low in productivity since they require the large amount of exposure time. A transfer type each-side exposure apparatus which is equipped with a plurality of light sources to effect exposure of each side of exposure material through one transfer thereof has been developed for purpose of eliminating said drawback. This exposure apparatus, however, also has problems to be solved.
Usually, in the transfer type each-side exposure apparatus, the size thereof is determined depending upon the irradiation area for permitting exposure to be made. Even when the irradiation area is made large, however, the apparatus per se is attempted to be minimized and thereby reduced in space therefor. For this reason, the exposure light sources are disposed at positions to vertically oppose each other with the exposure material located therebetween and to be substantially equally spaced from the exposure material. Whereby, those light sources are lit on a continuous basis. The exposure material is transferred into an exposure chamber and is moved through an exposure zone therein. For this reason, occasionally, the exposure material is discontinuous between the upper and lower light sources, so that the two light sources, while lit, oppose each other with nothing intervening in between. The light sources are provided with reflectors which optically form elliptic or parabolic faces, each reflector being disposed such that a light emitting portion of the corresponding light source is located on one focal point of the reflector. Therefore, when, as mentioned above, the light sources have been made directly to oppose each other while they are being lit, the light beams made parallel to each other by one reflector enter the other opposing reflector and are focussed onto a cathode constituting the light emitting portion of the light source having the other opposing reflector. As a result, the cathode, undesirably, is burnt or deteriorated.